Non-magnetic pair-breaking effect on La(Fe_{1-x}Zn_{x})AsO_{0.85} studied by NMR and NQR

TL;DR

This study investigates how non-magnetic Zn impurities suppress superconductivity in LaFeAsO$_{0.85}$ without altering its normal-state electronic properties, highlighting a pair-breaking mechanism.

Contribution

It provides microscopic evidence that Zn acts as a strong non-magnetic pair-breaker in LaFeAsO$_{0.85}$, decoupling normal-state properties from superconductivity suppression.

Findings

Superconductivity disappears with 3% Zn substitution.

Normal-state NMR/NQR spectra remain unchanged despite Zn doping.

Zn induces a strong non-magnetic pair-breaking effect.

Abstract

$^{75}$As and $^{139}$La NMR and nuclear quadrupole resonance (NQR) studies on Zn-substituted LaFeAsO$_{0.85}$ have been performed to investigate the Zn-impurity effects microscopically. Although superconductivity in LaFeAsO$_{0.85}$ disappears by 3% Zn substitution, we found that NMR/NQR spectra and NMR physical quantities in the normal state are hardly changed, indicating that the crystal structure and electronic states are not modified by Zn substitution. Our results suggest that the suppression of superconductivity by Zn substitution is not due to the change of the normal-state properties, but due to strong non-magnetic pair-breaking effect to superconductivity.